As recently demonstrated in this laboratory, the dampening of the IgE response by conjugates of common allergens with the monomethoxy derivatives of polyethylene glycol (mPEG) appears to be due to the activation of suppressor T (TS) cells. Since, according to the present consensus, TS cells carry markers coded by the I-J region of the major histocompatibility complex of the mouse, an attempt will be made to isolate these cells with insolubilized monoclonal anti-I-J serum. The putative TS cells, isolated by this method, will be analyzed for the presence of receptors for the specific antigens used for their induction. If functionally distinct subpopulations of T cells regulating the IgE response can be isolated in this way, attempts will be made to establish if these cells are Ly 1 or Ly 23. Xenogeneic or monoclonal antibodies will be produced to the suppressive factor which is released by TS cells. For this purpose, subpopulations of T cells, isolated as described above, will be subjected to rapid freezing and thawing (F/T) and the F/T supernatant, instead of whole cells, will be transferred into recipients. If suppressor (or amplifier) factors can be identified in this way, they will be characterized as to molecular size by gel filtration, antigen specificity, susceptibility to proteolytic enzymes, and H-2 specificity. In a parallel project, an attempt will be made to produce a highly specific antibody preparation to monoclonal murine IgE for the development of a radioallergosorbent test (RAST) for mouse IgE. In an effort to investigate the genetic control regulating the induction and maintenance of IgE antibody synthesis: (i) the role of Ia antigens and macrophage factors will be examined, (ii) an analysis of the idiotypes of the IgE antibodies and of appropriate T cell factors will be performed using the anti-GT and anti-GAT IgE model, (iii) attempts will be made to identify the sites on the molecule of an antigen responsible for the activation of helper or suppressor cells, and (iv) the gene loci controlling the expression of a given spectrotype will be mapped and the influence of MHC genes and IgE regulator genes will also be investigated.